ET = 40 volts + 60 volts + 100 volts

ET = 200 volts

When you use Ohm's law, the quantities for the

equation must be taken from the same part of the

circuit. In the above example, the voltage across R2

was computed using the current through R2 and the

resistance of R2.

The value of the voltage dropped by a resistor is determined by the applied

voltage and is in proportion to the circuit resistances. The voltage drops

that occur in a series circuit are in direct proportion to the resistances.

This is the result of having the same current flow through each resistor.

The larger the ohmic value of the resistor, the larger the voltage drop

across it.

(4) *Power in a Series Circuit.*

Each of the resistors in a series

circuit consumes power which is dissipated in the form of heat. Since this

power must come from the source, the total power must be equal to the power

consumed by the circuit resistances. In a series circuit, the total power

is equal to the sum of the power dissipated by the individual resistors.

Total power (PT) is equal to:

PT = P1 + P2 + P3 + . . . Pn

Example: A series circuit consists of three resistors having values of 5

Ohms, 10 Ohms, 15 Ohms. Find the total power when 120 volts is applied to

the circuit (figure 25).

Given:

R1 = 5 Ohms

R2 = 10 Ohms

R3 = 15 Ohms

E = 120 volts

Solution:

RT = R1 + R2 + R3